Methods for Rapid Screening in Woody Plant Herbicide Development

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Methods for woody plant herbicide screening were assayed with the goal of reducing resources and time required to conduct screenings for new products. Past studies have demonstrated reductions in required screening resources (time, amount of herbicide active ingredient, and size of seedlings) can be achieved relative to field exclosure screenings. Rapid screening methods including, greenhouse seedling screening, germinal screening, and seed screening were performed using triclopyr and 8 experimental herbicides supplied by Dow AgroSciences (DAS). Five woody species were included in screenings: black locust, loblolly pine, red maple, sweetgum, and water oak. Two groups of seedlings were used in greenhouse screening: 1-year-old (1-0) and 2-year-old (2-0). Seedling age was not calendar years, but was the number of greenhouse growing seasons seedlings experienced prior to herbicide treatment. Height and mortality responses showed that 1-0 seedlings were more susceptible to herbicide injury than 2-0 seedlings. Significant linear regression models were produced correlating 1-0 seedling pre-dormancy with post dormancy responses, shortening the length of that screening to 11 weeks from treatment to results. Species and herbicide specific models were produced correlating 2-0 seedling responses to 1-0 seedling data, germinal responses to 1-0 seedling data, and seed responses to 1-0 seedling data. 1-0 seedling pre to post dormancy predictions were more successful than other models. Results suggest that rapid screening methods have some usefulness in early stages of product development to determine herbicide activity and spectrum of efficacy to guide planning of larger scale field trials, resulting in savings of time and resources.